Bonsai cultivation and care requires techniques and tools that are specialized to support the growth and long-term maintenance of trees in small containers.

Sources of bonsai material

All bonsai start with a specimen of source material, a plant that the grower wishes to train into bonsai form. Bonsai practice is an unusual form of plant cultivation in that growth from seeds is rarely used to obtain source material. To display the characteristic aged appearance of a bonsai within a reasonable time, the source plant is often mature or at least partially grown when the bonsai creator begins work. Sources of bonsai material include:

• Propagation from a source tree through cuttings or layering.
• Nursery stock directly from a nursery, or from a garden centre or similar resale establishment.
• Commercial bonsai growers, which, in general, sell mature specimens that display bonsai aesthetic qualities already.
• Collecting suitable bonsai material in its original wild situation, successfully moving it, and replanting it in a container for development as bonsai. These trees are called Yamadori and are often the most expensive and prized of all Bonsai.

Techniques

The practice of bonsai development incorporates a number of techniques either unique to bonsai or, if used in other forms of cultivation, applied in unusual ways that are particularly suitable to the bonsai domain. These techniques include:

• Leaf trimming, the selective removal of leaves (for most varieties of deciduous tree) or needles (for coniferous trees and some others) from a bonsai's trunk and branches.
• Pruning the trunk, branches, and roots of the candidate tree.
• Wiring branches and trunks allows the bonsai designer to create the desired general form and make detailed branch and leaf placements.
• Clamping using mechanical devices for shaping trunks and branches.
• Grafting new growing material (typically a bud, branch, or root) into a prepared area on the trunk or under the bark of the tree.
• Defoliation, which can provide short-term dwarfing of foliage for certain deciduous species.
• Deadwood bonsai techniques called jin and shari simulate age and maturity in a bonsai.

Care

Small trees grown in containers, like bonsai, require specialized care. Unlike houseplants and other subjects of container gardening, tree species in the wild, in general, grow roots up to several meters long and root structures encompassing several thousand liters of soil. In contrast, a typical bonsai container is under 25 centimeters in its largest dimension and 2 to 10 liters in volume. Branch and leaf (or needle) growth in trees is also large-scale in nature. Wild trees typically grow 5 meters or taller when mature, whereas the largest bonsai rarely exceed 1 meter and most specimens are significantly smaller. These size differences affect maturation, transpiration, nutrition, pest resistance, and many other aspects of tree biology. Maintaining the long-term health of a tree in a container requires some specialized care techniques:

• Watering must be regular and must relate to the bonsai species' requirement for dry, moist, or wet soil.
• Repotting must occur at intervals dictated by the vigour and age of each tree.
• Tools have been developed for the specialized requirements of maintaining bonsai.
• Soil composition and fertilization must be specialized to the needs of each bonsai tree, although bonsai soil is almost always a loose, fast-draining mix of components.^[83]
• Location and overwintering are also species-dependent, and it is important to note that few of the traditional bonsai species can survive inside a typical house.

A concept and early versions

The lineage of bonsai derives from the Chinese penjing.^[7] Imperial embassy personnel and Buddhist students from Japan had been returning from mainland China with many souvenirs, including occasional container planting, since the 6th century.^[8] At least 17 diplomatic missions were specifically sent from Japan to the Tang court between the years 603 and 839.^[8] From about the year 970 comes the first lengthy work of fiction in Japanese, Utsubo Monogatari (The Tale of the Hollow Tree), which includes this passage: "A tree that is left growing in its natural state is a crude thing. It is only when it is kept close to human beings who fashion it with loving care that its shape and style acquire the ability to move one." The idea, therefore, was already established by this time that natural beauty becomes true beauty only when modified in accordance with a human ideal.^[9]
Saigyo Monogatari Emaki was the earliest known scroll to depict dwarfed potted trees in Japan. It dates from the year 1195. Wooden tray and dish-like pots with dwarf landscapes on modern-looking wooden shelf/benches are shown in the 1309 Kasuga-gongen-genki scroll. These novelties show off the owner's wealth and were probably exotics imported from China.^[10]
With the extended invasion of the Mongol Empire into China, many artists and intellectuals found comfortable life and recognition in Japan where Song dynasty culture was still actively studied. Chinese Chan Buddhist monks came over to teach at monasteries, and one of the monks' activities was to introduce political leaders of the day to the various arts of miniature landscapes as ideal accomplishments for men of taste and learning.^[11][12]
The c.1300 rhymed prose essay, Bonseki no Fu (Tribute to Bonseki) written by celebrated priest and master of Chinese poetry, Kokan Shiren (1278–1346), outlined the aesthetic principles for what would be termed bonsai, bonseki and garden architecture itself. At first, the Japanese used miniaturized trees grown in containers to decorate their homes and gardens.^[12][13][14]
Criticism of the interest in curiously twisted specimens of potted plants shows up in one chapter of the 243-chapter compilation Tsurezuregusa (c.1331). This work would become a sacred teaching handed down from master to student, through a limited chain of poets (some famous), until it was at last widely published in the early 17th century. Before then, the criticism had only a modest influence on dwarf potted tree culture.
In 1351, dwarf trees were displayed on short poles as portrayed in the Boki Ekotoba scroll.^[15] Several other scrolls and paintings also included depictions of these kinds of trees. Potted landscape arrangements made during the next hundred years or so included figurines after the Chinese fashion in order to add scale and theme. These miniatures would eventually be considered garnishes decidedly to be excluded by Japanese artists who were simplifying their creations in the spirit of Zen Buddhism.^[16]

 Bonsai (help·info) (盆栽^?, lit. plantings in tray, from bon, a tray or low-sided pot and sai, a planting or plantings)^[1] is a Japanese art form using miniature trees grown in containers. Similar practices exist in other cultures, including the Chinese tradition of penjing from which the art originated, and the miniature living landscapes of Vietnamese hòn non bộ. The Japanese tradition dates back over a thousand years, and has its own aesthetics and terminology.
"Bonsai" is a Japanese pronunciation of the earlier Chinese term penzai. A "bon" is a tray-like pot typically used in bonsai culture.^[2] The word bonsai is often used in English as an umbrella term for all miniature trees in containers or pots, but this article focuses on bonsai as defined in the Japanese tradition.
The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower).^[3] By contrast with other plant cultivation practices, bonsai is not intended for production of food, for medicine, or for creating yard-size or park-size gardens or landscapes. Instead, bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container.
A bonsai is created beginning with a specimen of source material. This may be a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species^[4] that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai.
The source specimen is shaped to be relatively small and to meet the aesthetic standards of bonsai. When the candidate bonsai nears its planned final size it is planted in a display pot, usually one designed for bonsai display in one of a few accepted shapes and proportions. From that point forward, its growth is restricted by the pot environment. Throughout the year, the bonsai is shaped to limit growth, redistribute foliar vigor to areas requiring further development, and meet the artist's detailed design.
The practice of bonsai is sometimes confused with dwarfing, but dwarfing generally refers to research, discovery, or creation of plant cultivars that are permanent, genetic miniatures of existing species. Bonsai does not require genetically dwarfed trees, but rather depends on growing small trees from regular stock and seeds. Bonsai uses cultivation techniques like pruning, root reduction, potting, defoliation, and grafting to produce small trees that mimic the shape and style of mature, full-size trees.

The term ornamental plant is used here in the same sense that it is generally used in the horticultural trades. ^[1][2] The term largely corresponds to 'garden plant', though the latter is much less precise, as any plant may be grown in a garden.

For plants to be considered as ornamental, they may require specific work and activity by a gardener. For instance, many plants cultivated for topiary and bonsai would only be considered as ornamental by virtue of the regular pruning carried out on them by the gardener, and they may rapidly cease to be ornamental if the work was abandoned.
Ornamental plants and trees are distinguished from utilitarian and crop plants, such as those used for agriculture and vegetable crops, and for forestry or as fruit trees. This does not preclude any particular type of plant being grown both for ornamental qualities in the garden, and for utilitarian purposes in other settings. Thus lavender is typically grown as an ornamental plant in gardens, but may also be grown as a crop plant for the production of lavender oil.

Similarly certain trees may be called ornamental trees. This term is used when they are used as part of a garden or landscape setting, for instance for their flowers, their texture, form and shape, and other aesthetic characteristics. In some countries trees in 'utilitarian' landscape use such as screening and roadside plantings are called amenity trees.

Most commonly ornamental garden plants are grown for the display of aesthetic features including: flowers, leaves, scent, overall foliage texture, fruit, stem and bark, and aesthetic form. In some cases, unusual features may be considered to be of interest, such as the prominent and rather vicious thorns of Rosa sericea and cacti. In all cases, their purpose is for the enjoyment of gardeners, visitors, and/or the public.